1. Field
The present disclosure relates to a control apparatus for an internal combustion engine which achieves homogeneous lean combustion while utilizing intake flow such as tumble and swirl.
2. Description of the Related Art
A control apparatus for an internal combustion engine which has an air flow control valve such as a tumble control valve and a swirl control valve positioned in an intake ports and which controls intake air flow generated in a cylinders according to combustion status is conventionally known (e.g., refer to Patent Literature 1, i.e., Japanese Patent Application Laid-Open (kokai) No. 2005-180247 (especially, refer to [0016], [0017] and claim 4)). A combustion mode to achieve stratified combustion and a combustion mode to achieve homogeneous combustion, etc. are mainly known as combustion modes. The homogeneous combustion is a combustion mode which makes air-fuel mixture dispersed homogeneously in a cylinder burn. The stratified combustion is a combustion mode which forms air-fuel mixture whose fuel concentration is rich in the vicinity of a spark plug and which makes the air-fuel mixture burn. Homogeneously combustion in the case where an air-fuel ratio of the air-fuel mixture is the theoretical air-fuel ratio is referred to as “homogeneous stoichiometric combustion.” Further, in the case where the air-fuel ratio of air-fuel mixture in a cylinder is lean air-fuel ratio (i.e., air-fuel ratio which is greater than the theoretical air-fuel ratio), homogeneous combustion and stratified combustion are referred to as “homogeneous lean combustion” and “stratified lean combustion” respectively.
Specifically, apparatus disclosed in the Patent Literature 1 (hereinafter, referred to as a “conventional apparatus”) is configured to change opening of a tumble control valve according to engine rotational speed and engine load in the case where a combustion mode is the homogeneous stoichiometric combustion. Thereby, it is possible to change flow speed of the tumble flow in a cylinder according to the engine rotational speed and the engine load. Thus, it is possible to keep combustion stability and combustion efficiency high during the homogeneous stoichiometric combustion.